Flame retardant cellulosic materials

ABSTRACT

Cellulosic materials such as paper, wood, cotton, rayon and the like are rendered flame retardant by the intimate association therewith of an effective flame retardant amount of a reaction product of aqueous solution of phosphoric acid or an acid ammonium phosphate and an alkylene oxide e.g., ethylene oxide. Amounts of said reaction product of at least, and preferably in excess of, 0.5 percent by weight are generally effective to render the cellulosic material flame retardant. Preferably the reaction product is rendered neutral before or after application to the cellulosic material in order that the material be rendered non-corrosive and non-irritating in nature.

Hi ti -15117 5g;

itemize?" United S1314 .X 30 35? Miller 1 FLAME RETARDANT CELLULOSICMATERIALS George T, Miller, Lewiston, N.Y.

[73] Assignee: Hooker Chemicals & Plastics Corporation, Niagara Falls,NY.

[22] Filed: Oct. 12, 1973 [21] Appl. No.: 405,962

[75] Inventor:

[52] US. Cl. ..106/15 FP; 117/137; 117/143 R;

117/147; 111/152; 117/154; 162/159 [51] Int. Cl C09d 5/18 [58] Field ofSearch 117/136, 137, 152, 154,

117/143 R, 147; 106/15 FP; 252/81; 260/953, 944, 948

3,369,060 2/1968 Pelletier et a1 260/933 Primary Examiner-William D.Martin Aizs'z'srant ExaminerTheodore G. Davis Attorney, Agent, orFirm-Peter F. Casella; Donald C. Studley; William J. Crossetta, Jr.

[5 7 4 ABSTRACT Cellulosic materials such as paper, wood, cotton, rayonand the like are rendered flame retardant by the intimate associationtherewith of an effective flame retardant amount of a reaction productof aqueous solution of phosphoric acid or an acid ammonium phosphate andan alkylene oxide e.g., ethylene oxide. Amounts of said reaction productof at least, and preferably in excess of, 0.5 percent by weight aregenerally effective to render the cellulosic material flame retardant.Preferably the reaction product is rendered neutral before or afterapplication to the cellulosic material in order that the material berendered noncorrosive and non-irritating in nature.

13 Claims, N0 Drawings FLAME RETARDANT CELLULOSIC MATERIALS Fl ELD OFINVENTION The invention relates to improvements in the art of renderingcellulosic materials flame retardant. More particularly it relates tothe treatment of cellulosic materials such as paper, wood, cotton, rayonand the like, with effective fire retardant amounts of a reactionproduct of aqueous solutions of phosphoric acid or an acid ammonium saltthereof with an alkylene oxide.

BACKGROUND OF THE INVENTION Cellulosic materials such as paper, wood,and cotton textiles, are highly flammable substances and once ignitedcontinue to burn. Methods for the flame proofing of these materials areknown but such methods are either too costly for general commercial use,relatively ineffective, or give rise to products having poor surfacecharacter.

With particular reference to paper, methods involving the application ofsalts of phosphoric acid, boric acid and sulfamic acid are, or havebeen, used. These methods while commercially attractive, costwise, aretroublesome due to the crystallization of such salts on the treatedmaterial after drying. Further, the salts crystallize on the applicationequipment necessitating the frequent shut down of such equipment forcleaning.

Organo phosphorus compounds, such as ,te tg is (alpha hydroxyethyl)phosphoni urn chloride a nd vari dii s deriva'tives" thereo'tfhaveal'sobeen suggested for the flame proofing of cellulosic materials. Suchcompounds provide a level of flame retardancy which is at leastequivalent to that obtained with the aforementioned phosphate and boratesalts. Moreover, the organo phosphorus compounds provide a durable flameretardant character which withstands repeated laundering and drycleaning. Such compounds, however, because of their relatively highcost, are economically feasible salts only where a durable finish isrequired.

Accordingly it can be seen that a need exists for a low cost effectivemethod for rendering cellulosic materials fire retardant which methodsdo not deleteriously affect'the surface characteristics of the treatedmaterial.

OBJECTS OF THE INVENTION It is, therefore, a principal object of thisinvention to devise improved fire retardant cellulosic materials.

Another object is to provide a process for treating cellulosic materialsto render them non-corrosive and non-irritating as well as flameretardant.

A particular object is to devise compositions comprising a cellulosicmaterial and an effective fire retardant amount of a reaction product ofaqueous phosphoric acid and an alkylene oxide intimately associatedtherewith.

These and other objects of the present invention will be obvious fromthe following description.

BRIEF SUMMARY OF INVENTION In accordance with the present invention,cellulosic materials are rendered fire retardant by intimately admixingthe material with an effective fire retardant amount of a reactionproduct of an aqueous phosphoric acid and an alkylene oxide. Theresultant product is preferably rendered neutral in character andthereafter dried to yield a product which not only is surprisingly fireretardant, non-corrosive and non-irritating in character but also has apleasant surface character, i.e., hand".

By effective flame retardant amount" is that amount of said reactionproduct which suffices to impart flame retardant character to thecellulosic material as defined by the American Society of TestingMaterials Test Standard D-777-46 and/or TAPPI Standard Test T-46l.

The term Oxygen Index as used herein below is that value determined inaccordance with the testing procedure described in The Oxygen FlameFlammability Test" J. L. Isaacs, J. Fire and Flammability Vol. 1 (Jan.I970, page 36 et seq.).

The materials treated in accordance with the present invention may beformed in part or in whole of cellulosic materials such as paper, wood,cotton and rayon and may be in various forms such as wood pulp, textilefibers or sheet goods. The materials can also be in comminuted forme.g., paper pulp, cotton fibers, etc. nonwoven form, e.g. paper sheets,wood boards, woven form, e.g., cotton or rayon textile sheeting, and thelike. Accordingly although, hereinafter, primary reference will be madeto the treatment of sheets of paper, this is not to be taken as alimitation as other forms of cellulosic material may be utilized as thematerials treated in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION- In accordance with a preferredmode of carrying out the present invention cellulosic materials, asabove defined, are intimately associated with an effective flameretardant amount of a reaction product of an aqueous solution ofphosphoric acid or an acid ammonium salt thereof and an alkylene oxide.Thereafter the treated material is contacted with an alkaline material,e.g., ammonia, ammonium hydroxide, organic amines such as ethyl amine,ethylene diamine and the like, to render the treated materialsubstantially neutral, i.e., a pH of about 6 to 7.5. Alternatively thereaction product, prior to association with the cellulosic material, maybe neutralized and thereafter utilized as a substantially neutralsolution.

The fire retardant treatment of the invention can be accomplished byseveral means. For example, the cellulosic material, in finished orunfinished condition, can be immersed, padded, sprayed, dipped orotherwise admixed with the aqueous reaction product, the thoroughlywetted or intimately associated mixture dried to remove excess moistureand then exposed to gaseous ammonia vapors until the treated materialreacts substantially neutral. The treated cellulosic material may beheated to below its decomposition temperature without significant effecton the treatment.

Alternatively the material can be intimately associated with an aqueoussolution of the substantially neutral reaction product to thoroughlyimpregnate the cellulosic material. Thereafter the treated materialcontaining an effective fire retardant amount of the neutralizedreaction product can be dried in any convenient manner.

The reaction product used in the process of this invention is a complexmixture of unknown composition and is obtained by reacting an alkyleneoxide e.g., ethylene oxide, 1,2-propylene oxide, 2,3butylene oxide, andthe like with an aqueous solution of a phosphoric acid, such as orthophosphoric acid, meta phosphoric acid, pyrophosphoric acid, and thelike, or an acid ammonium salt thereof such as monoammonium orthophosphoric acid, diannnonium orthophosphoric acid, monoammoniummeta-phosphoric acid, and the like.

The preferred reactants are ortho phosphoric acid or diammonium acidortho phosphate, and ethylene oxide because of their overalleffectiveness and low cost.

Aqueous solutions of the phosphoric acid or ammonium salts thereof areused. Such solutions may contain from about 5 to about 85 percent byweight of 100% phosphoric acid (or the equivalent amount of the acidammonium phosphate) although preferably dilute solutions containing fromabout 7 to about 25 percent of 100% phosphoric acid are used.

To carry out the preparation of the said reaction product, an aqueoussolution of the phosphoric acid or acid ammonium salt thereof is placedin a suitable reactor which may be equipped with an agitator and thealkylene oxide is bubbled into the solution. The initial exotherm may becontrolled by cooling the mixture and- /or by adjusting the rate ofaddition of the alkylene oxide. The temperature of the reaction isadjusted to from about 0 to about 100 centigrade and preferably fromabout 10 to about 80 centigrade and an amount of the alkylene oxidewhich is from about one-half to about one and one half times the weightof 100 percent phos phoric acid, or its equivalent, present. Preferablyfrom about one to about one and one-half the weight of 100% phosphoricacid equivalent is added. The resultant solution can be used directlybut preferably it is neutralized to a pH of about 6.0 to about 7.5 orhigher, with ammonia or other alkaline reacting substances, as

defined above.

The resulting aqueous solution of the reaction product is a rathercomplex mixture which does not crystallize on standing or onevaporation, or if crystals do form they are rather minimal in amount.Thus the reac tion product is a liquid to a fluid slurry even afterdrying. The reaction product is substantially neutral or can be renderedneutral in situ or after application to the cellulosic material. Such acomposition is eminently advantageous since it can be more effectivelyapplied to and distributed throughout the material than a compositionwhich crystallizes on drying and thus deposits isolated crystals on thematerial thereby affecting the surface character, e.g., hand, of thetreated material.

Without being bound by any theory or explanation of the reactions whichtake place during the formation of the reaction product of the aqueousphosphoric acid or acid ammonium salt thereof and alkylene oxide, it isbelieved that when reacting, for example, ethylene oxide and aqueousortho phosphoric acid a major amount of a hydroxy ethyl ester of orthophosphoric acid is formed together with lesser amounts of ethyleneglycol and other phosphorus containing organic compounds. Also there maybe more or less amounts of unreacted phosphoric acid ions present whichupon neutralization with ammonia or ammonium hydroxide form ammoniumphosphates. Such a complex mixture, fortuitously, resistscrystallization even when dried to a low water content, and thusprovides not only an effective fire retardant agent, but also anon-irritating, i.e., non-acidic, which can be readily applied tocellulosic materials and dried thereon without affecting the surfaceproperties, e.g., hand, of the thus treated material.

The present invention can be most advantageously utilized for impartingflame retardant character to paper and paper products either at the pulpstage or finished stage in such products as crepe or tissue paper usedfor decorative purposes and the like. The aqueous reaction product canalso be used to treat Christmas trees by dipping, spraying and the like,to make the trees fire retardant. Further as has been discovered byanother, the aqueous solution is a highly effective flame retardantmaterial which can be used to combat forest fires. In such applications,additives such as jaguar gums to regulate viscosity, wetting agents,iron oxides and other coloring agents, other flame retardant additivessuch as antimony oxides, can be dissolved or suspended in the aqueoussolution. This then can be used to spray the burning area and/or limitthe burning area by spraying the area adjacent thereto and thereby toprevent or to limit the fire. On evaporation of the water from thesolution a viscous liquid remains which adheres to and coats the treesand effectively renders them flame retardant.

The following examples will illustrate the present invention. Parts andpercentages are by weight and temperatures are given in degreesCentigrade.

EXAMPLE l Preparation of Reaction Product of Aqueous Phosphoric Acid andEthylene Oxide A mixture of58.5 parts of 85% ortho phosphoric acid wasdiluted to 500 parts with water. The solution has a specific gravity of1.055 at 25 degrees. Ethylene oxide was bubbled into the solution forabout 10 minutes. The solution gained 75.7 parts in weight and had aspecific gravity of 1.073 at 25. This was a 15% solution of the reactionproduct.

The above procedure was repeated but ethylene oxide was bubbled into thesolution for only about four minutes. The resulting solution gained only37.0 parts and had a specific gravity, at 25, of 1.064. This was a 7%solution of the reaction product.

In a similar manner, ethylene oxide was bubbled into a 10% phosphoricacid solution for about three minutes to give a gain in weight of 20.5parts and a specific gravity (25) of 1.0595. This was a 4% aqueoussolution of the reaction product.

In a similar manner, ethylene oxide was bubbled into a 10% aqueoussolution of phosphoric acid for about eight minutes, to give an 11%solution of the reaction product. The gain in weight was 54.9 parts,final temperature 77, and the specific gravity (25) was 1.068.

EXAMPLE 2 A two inch wide strip of tissue paper (Kim-Wipe") was immersedin an aqueous solution of the reaction product of ortho phosphoric acidand ethylene oxide containing 4% of said reaction product and preparedas described in Example 1 above. The impregnated tissue paper was laidon a metal plate and covered with a piece of filter paper and a papertowel. the sandwich" was squeezed dry" by rolling. The tissue paper wasthen placed in a oven until dry. The tissue paper was tested accordingto ASTM D-777-46 and found to be fire retardant (char length 4 inches).The hand of the treated tissue paper was excellent and its strength waspractically unaffected by the treatment.

EXAMPLE 3 Swatches of cotton cheese cloth and cotton sheeting wereimmersed in an aqueous solution of the reaction product of phosphoricacid and ethylene glycol containing of the reaction product and preparedas described in Example 1 above. The solution was neutralized to a pH of6.9 with ammonium hdyroxide. The swatches were squeezed out manually andthen dried in a 70 oven.

The Oxygen Index of the treated cotton swatches was 3536 (OI ofuntreated cotton is 19) and strips of each of the treated cottonswatches exposed to a vertical flame was self extinguishing with a 3-3/2 inch char length.

EXAMPLE 4 To a solution of 58.5 parts of 85% ortho phosphoric aciddiluted to 500 parts with water, ethylene oxide was added. The latterwas bubbled into the acid solution at such a rate that the temperaturedid not exceed about 50. After the addition of about 75 parts ofethylene oxide, the addition was completed. The reaction mixture wasagitated for about 5 minutes and then rendered neutral (pH of about 7)by the addition of ammonium hydroxide.

Tissue paper was impregnated with this solution by placing a sheet ofthe paper on a 6 inch metal plate and lowering the plate into a traycontaining the solution. The paper swelled and floated in the solution.Thereafter the metal plate was raised with a slight slant to remove theimpregnated paper. The tissue paper was covered with a sheet of filterpaper and then several paper towels were laid on the filter paper. Theresulting sandwich was rolled with a heavy roller to squeeze excesssolution out of the tissue paper. The tissue paper was placed in a 40oven for about 1 hour and then hung in the air at about 23 and 51% R.H.for about one hour. The treated dried and equilibrated tissue paper wasthen tested for flame retardancy according to TAPP!- T-46l and found tobe flame retardant. The tests were made with strips of treated paper cutboth parallel and perpendicular to the screen. Single thickness anddouble thickness tissue papers were tested and found to be flameretardant.

EXAMPLE 5 A solution of 50 parts of diammonium acid phosphate in 450parts of water was cooled to about 0 in an ice bath. Ethylene oxide wasbubbled into the solution until about 50 parts were added. The ethyleneoxide was absorbed rapidly and the temperature of the aqueous reactionmixture rose to about 13. The solution was placed in a stoppered bottleand permitted to stand for about 24 hours at ambient temperature. Thesolution remained clear and free of crystals. A small portion of theaged solution was placed on a metal plate and evaporated in an oven. Thesolution did not crystallize and a thick oily mass remained.

Strips of tissue paper were impregnated with the aged solution by themethod described in Example 4 above and then tested for flame retardancyaccording to TAP- P1-T-46l. The treated tissue paper was found to beflame retardant by this standard test procedure.

The invention has been described in the above specification andillustrated by reference to specific embodiments in the illustrativeexamples. However, it is to be understood. that this not be so limitedsince changes and modifications in the specific details disclosed hereinabove can be made without departing from the scope or spirit of theinventions disclosed herein.

What is claimed is:

1. Fire retardant cellulosic containing material which material containsan effective fire retardant amount of a reaction product of aqueousortho phosphoric acid or an acid ammonium salt thereof and an alkyleneoxide wherein said reaction product has been obtained by re acting anaqueous solution of a ortho phosphoric acid or an acid ammonium saltthereof containing from about 1 to about percent by weight of orthophosphoric acid or the equivalent amount of an acid ammonium saltthereof with an amount of an alkylene oxide which is from about 0.5 to1.5 times the weight of percent phosphoric acid or equivalent thereofpresent, intimately associated therewith.

2. Fire retardant cellulosic material as claimed in claim 1 wherein thematerial is paper.

3. Fire retardant cellulosic material as claimed in claim 1 wherein thematerial is cotton.

4. Fire retardant cellulosic material as claimed in claim 1 wherein thematerial comprises at least 0.5 percent by weight of the reactionproduct of aqueous phosphoric acid and an alkylene oxide.

5. Fire retardant cellulosic materials as claimed in claim 1 wherein thealkylene oxide is ethylene oxide.

6. The fire retardant material of claim 1 wherein the aqueous phosphoricacid solution contains from about 7 to about 25 percent by weight ofphosphoric acid.

7. The fire retardant material of claim 1 wherein the solution of thereaction product contains from about 7 to about 1 l percent by weight ofthe reaction product.

8. Flame retardant cellulosic material as claimed in claim 4 whereinsaid reaction product has been neutralized with an alkaline reactingsubstance of the group consisting of ammonia and organic amines.

9. Fire retardant cellulose materials as claimed in claim 4 wherein thealkylene oxide is ethylene oxide.

10. Fire retardant cellulosic materials as claimed in claim 4 whereinsaid material is paper.

11. Fire retardant cellulosic materials as claimed in claim 4 whereinsaid material is cotton.

12. The fire retardant material of claim 5 wherein sufficient ethyleneoxide is reacted with the phosphoric acid to yield a solution containingfrom about 4 to about 15% by weight of the reaction product.

13. The fire retardant material of claim 8 wherein the aqueous reactionproduct is rendered neutral with am

1. FIRE RETARDANT CELLULOSIC CONTAINING MATERIAL WHICH MATERIAL CONTAINSAN EFFECTIVE FIRE RETARDANT AMOUNT OF A REACTION PRODUCT OF AQUEOUSORTHO PHOSPHORIC ACID OR AN ACID AMMONIUM SALT THEREOF AND AN ALKYLENEOXIDE WHEREIN SAID REACTION PRODUCT HAS BEEN OBTAINED BY REACTING ANAQUEOUS SOLUTION OF A ORTHO PHOSPHORIC ACID OR AN ACID AMMONIUM SALTTHEREOF CONTAINING FROM ABOUT 1 TO ABOUT 85 PERCENT BY WEIGHT OF ORTHOPHOSPHORIC ACID OR THE EQUIVALENT AMOUNT OF AN ACID AMMONIUM SALTTHEREOF WITH AN AMOUNT OF AN ALKYLENE OXIDE WHICH IS FROM ABOUT 0.5 TO1.5 TIMES THE WEIGHT OF 100 PERCENT PHOSPHORIC ACID OR EQUIVALENTTHEREOF PRESENT, INTIMATELY ASSOCIATED THEREWITH.
 2. Fire retardantcellulosic material as claimed in claim 1 wherein the material is paper.3. Fire retardant cellulosic material as claimed in claim 1 wherein thematerial is cotton.
 4. Fire retardant cellulosic material as claimed inclaim 1 wherein the material comprises at least 0.5 percent by weight ofthe reaction product of aqueous phosphoric acid and an alkylene oxide.5. Fire retardant cellulosic materials as claimed in claim 1 wherein thealkylene oxide is ethylene oxide.
 6. The fire retardant material ofclaim 1 wherein the aqueous phosphoric acid solution contains from about7 to about 25 percent by weight of phosphoric acid.
 7. The fireretardant material of claim 1 wherein the solution of the reactionproducT contains from about 7 to about 11 percent by weight of thereaction product.
 8. Flame retardant cellulosic material as claimed inclaim 4 wherein said reaction product has been neutralized with analkaline reacting substance of the group consisting of ammonia andorganic amines.
 9. Fire retardant cellulose materials as claimed inclaim 4 wherein the alkylene oxide is ethylene oxide.
 10. Fire retardantcellulosic materials as claimed in claim 4 wherein said material ispaper.
 11. Fire retardant cellulosic materials as claimed in claim 4wherein said material is cotton.
 12. The fire retardant material ofclaim 5 wherein sufficient ethylene oxide is reacted with the phosphoricacid to yield a solution containing from about 4 to about 15% by weightof the reaction product.
 13. The fire retardant material of claim 8wherein the aqueous reaction product is rendered neutral with ammonia.